Field of the Invention
The present invention relates to an apparatus and method for driving a touch sensor, and more particularly, to an apparatus and method for driving a touch sensor, which is capable of improving touch sensitivity and accuracy by adaptively setting a secondary reference value of each touch node and determining presence/absence of a touch operation.
Discussion of the Related Art
Today, touch sensors capable of inputting information through touch on screens of various display apparatuses have been widely used as an information input apparatus of a computer system. Since a touch sensor moves or selects display information by touching a screen using a finger or a stylus, all people may easily utilize the touch sensor.
An apparatus for driving a touch sensor detects touch generated in the touch sensor on a display apparatus and a touch position and outputs touch information and a computer system analyzes the touch information and executes a command. As a display apparatus, a liquid crystal display apparatus, a flat display apparatus such as a plasma display panel, an organic light emitting diode display apparatus, etc. is mainly used. As touch sensor technology, a resistive method, a capacitive method, an optical method, an infrared method, an ultrasonic method, an electromagnetic method, etc. may be used according to sensing principles.
The touch sensor is manufactured in the form of a panel and is composed of an on-cell touch sensor attached to an upper portion of a display apparatus or an in-cell touch sensor mounted in a pixel matrix of a display apparatus. As a touch sensor, a photo touch sensor for detecting touch according to optical power using a photo transistor and a capacitive touch sensor for detecting touch according to capacitive change are mainly used.
In general, in an apparatus for driving a touch sensor, a read-out integrated circuit (IC) drives a touch sensor and detects raw data using a read-out signal received from the touch sensor. A micro control unit (MCU), which is a signal processor, compares the raw data with a reference signal, determines presence/absence of a touch operation, calculates touch coordinates, and transmits the touch coordinates to a host computer. The host computer executes a command corresponding to the touch coordinates.
In a display apparatus having a touch sensor, a noise component generated in the display apparatus is introduced into the touch sensor to be included in a read-out signal of the touch sensor. Although a noise filter for reducing a noise component is used, a noise component remains in raw data. Since the noise component of the display apparatus is changed according to images, raw data detected from a read-out signal of a touch node is also changed according to frames. In addition, raw data of each touch node may be changed according to external environmental conditions of a touch sensor and positions of a touch node.
However, since a conventional MCU compares raw data of each touch node with the same predetermined reference value and determines presence/absence of a touch operation, if raw data is changed according to noise of a peripheral environment, a touch operation may not be detected. Thus, touch sensitivity and accuracy may be deteriorated.